1. Field of the Invention
The present invention relates generally to an automatic document feeder (ADF), an image reading device including the ADF, and an image forming apparatus including the ADF. More particularly, the invention relates to an ADF that automatically conveys original document sheets one sheet by one sheet from a stack of the document sheets placed on a document tray, an image reading device and an image forming apparatus such as a facsimile, a copier, a multifunction peripheral including the ADF.
2. Description of the Related Art
This type of automatic document feeder generally employs a DC motor as a driving source. This is because using a DC motor as the driving source allows reducing power consumption as compared with using an AC motor as the driving source.
Such an ADE typically adopts a safety measure e.g., blocking power supply to a DC motor at jam recovery. More specifically, in such an ADF, an original document (hereinafter, “document”) can be jammed into a component (e.g., a conveying roller), causing paper jam (document jam) to occur. Causes of the paper jam include a stapled document, a bent document, and variation in document type, such as a size, a thickness, or a material. When paper jam occurs, a user performs so-called jam recovery in which a user opens a document feed cover of the ADF and removes a jammed document. An ADF generally includes an open/close detection sensor that detects an open/closed state of the document feed cover. During jam recovery, power supply to the DC motor is blocked in response to detecting that the document feed cover is in the open state based on a detection output of the open/close detection sensor. As a result, a user can perform jam recovery safely.
Meanwhile, in a conventional ADF, there can occur a situation that a document feed cover is not completely closed, or, in other words, a semi-locked state (halfway-closed state) can occur.
There is disclosed an ADE that detects occurrence of such a semi-locked state using an open/close detecting unit and a document-loading detecting unit to thereby increase accuracy in detecting a semi-locked state of a top cover. An example of such an ADF is disclosed in Japanese Laid-open Patent Application No. 2011-191630.
The ADF disclosed in Japanese Laid-open Patent Application No. 2011-191630 is configured to detect an open/closed state of the top cover at two positions by arranging, in a main body of the ADF, the open/close detecting unit on one side in an axial direction of a rotary shaft of the top cover and the document-loading detecting unit on the other side.
Adopting an interlock switch that blocks power supply to the driving source when an opening/closing unit is opened can increase safety level. However, in an ADF adopting such an interlock switch, when results of open/close detection disagree between the open/close detection sensor and the interlock switch, an erroneous determination can be made that, for example, a machine anomaly has occurred.
The open/close detection sensor is configured to detect an open state of the opening/closing unit and, upon detection of the open state, the ADE is brought to a standby mode where the ADF is deactivated. The interlock switch is switched off when the opening/closing unit is open, and blocks power supply to the driving source.
More specifically, mounting the interlock switch on the ADF allows blocking power supply to the driving source immediately when the opening/closing unit is opened. As a result, user safety during jam recovery can be further increased.
However, combined use of the open/close detection sensor and the interlock switch can be disadvantageous in the following way. In a situation where, for instance, the interlock switch is off even though the opening/closing unit is detected as being in the closed state according to a detection output of the open/close detection sensor, whereas a notification about the closed state (i.e., exit from the standby mode) according to the open/close detection sensor is sent to a user, power supply to the driving source is blocked by the interlock switch. As a result, it is occurred an abnormal condition in which the ADF does not operate even though the opening/closing unit is closed.
As described above, when both the open/close detection sensor and the interlock switch that blocks power supply to the driving source when the opening/closing unit is opened are mounted on the ADF, the ADF can be misjudged as being possibly anomalous in a case where the open/closed state of the opening/closing unit is erroneously detected.
In light of the foregoing, there is a need for an ADE capable of resolving a trouble that can occur when both the open/close detection sensor and the interlock switch are mounted on the ADF and that arises from erroneous detection of the open/closed state of the opening/closing unit, thereby increasing reliability of the ADF, an image reading device including the ADF, and an image forming apparatus including the same.
It is an object of the present invention to at least partially solve the problem in the conventional technology.